Sorry I don't remember the details and I'm just about to rush out of the house, but in a recent thread in the Cold Waters discussion group over on Steam, KFG pointed to the txt control file that controls the sonar signatures displayed on the signature panel.
Here is the thread:
https://steamcommunity.com/app/54121...0619111656768/
You are looking for the THEATRE_sea_traffic.txt file in the default/campaign/maps folder.
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